This invention relates to apparatus for separating successive sets of sheets from a copier or printer and, especially, to such apparatus for separating successive sets of copy sheets from an electrophotographic copier.
Electrophotographic copiers which feed individual sheets of a stack of originals to an exposure platen a multiple number of times in recirculating fashion to produce collated sets of copies are known in the art. It is desirable that copiers of this type provide some means for facilitating the ready separation of individual collated sets of copies. One method of separating sets of copies known in the art, disclosed, for example, in U.S. Pat. No. 3,964,741 issued to Kroeker, is to feed copy sheets along a fixed feed path and shift the position of the copy tray between successive sets of copies to provide the desired offset. Such a method, however, has several disadvantages. First, since the tray may typically accommodate several hundred sheets, the mechanical assembly required to shift the tray back and forth in an accurate manner can be quite complex and expensive. Second, the size of the copying machine is undesirably increased because of the bulk of the shifting assembly. Third, the continual jarring of the sets of copies already stacked as the copy tray is shifted tends to disturb the alignment of the sheets in the tray, making their ready separation more difficult.
U.S. Pat. No. 3,630,607 issued to Korn et al discloses a copy sheet set separator for an electrophotographic copier in which a gate is selectively moved across the exit feed path to form an escrow area for accumulating sheets belonging to successive sets. Rotating elastomer vanes urge the sheets entering the escrow area transversely against a limit stop which alternates between two transversely spaced positions for successive sets of sheets. When an entire set has accumulated in the escrow area, the gate is retracted from the feed path and a pair of feed rollers move into engagement with the set to deliver it to a stacking tray. While the system shown in this patent avoids some of the defects referred to above, the complexity of the disclosed system and the necessity of accumulating an entire set of sheets before delivery of the first sheet are obvious disadvantages.